The relationship between vascular thrombosis and malignant disease has been repeatedly confirmed. A substance that diffuses from malignant tissue and promotes blood coagulation, cancer thrombogenic factor (CTF) has been partially purified and characterized. It is a proteolytic lipoprotein that does not promote coagulation via either the intrinsic (via Factor VIII) or the extrinsic (via Factor VII) pathway. It is inhibited by diisopropylfluorophosphate (DFP), unlike normal tissue thromboplastin which is insensitive to DFP. The research will study the activation of Factors X and II by CTF to try to establish the site of action within the blood coagulation scheme. CTF will be further purified and characterized with the use of artificial proteolytic substrates.